I went over an unexpected curb as I pulled into the Paint Store parking lot to check my location.
I landed hard, but didn't think it was that hard... After checking Maps, I went to pedal away... Only to discover the rear tire completely flat -- D'oh! Time to check the iPhone for nearby bike stores with patch kits.
Finally got a spare tube and discovered the problem:
That's an inch long screw -- totally through the tire and the tube... The only thing funnier would've been if it had a Pentalobe head.
On the bright side, I know exactly where to patch it!